Agreed, so my question is why the OP is declaring 2 party system as "worse" when all current systems have drawbacks.

Worse is subjective in this arena. So what are your metrics? What do you define as better? I'm not terribly keen on prop rep, for example - I think it actually gives too much power to extreme parties. Maybe you disagree. Maybe you think it would be better? If so, why?

This is a common argument. For example, many people in the UK's Labour party said this would be the case if the UK moved away from FPTP to AV. The conservatives wouldn't even allow the choice of real PR, limiting the vote to either what they wanted or a crap choice that no-one wanted in an attempt to get their policy choices rubber stamped with a false sense of public approval. This "worked" for that vote, and for Scottish Independence (not allowing further devolution as an option which would have won handily) and failed catastrophically with Brexit.

Notably, Brexit was caused by the small party UKIP stealing votes from the Conservatives, and then by Lib-Dem voters fleeing to Labour because they previously teamed up with the Conservatives. So a leftward shift of voters, sent the result rightward, giving the Conservatives a clear victory which meant they had to deliver a referendum that they never thought they'd have to.

Too late now to change it, but it seems likely the UK wouldn't be tearing itself apart at the moment with a better system.

I'm OP. I just said why the 2 party system is worse. Re-read my previous comment.